: The objective of this proposal is to generate data that can be useful in determining how system perturbations, such as hypoxia, gasping, and vagal and peripheral chemoreceptor activities, result in changes in respiratory patterns during maturation. The phrenic neurogram will be assessed as it exhibits features that reflect the dynamics of the phrenic respiratory pattern generator. The investigators will employ a technique known as non-linear neural dynamical analysis as a useful measure of quantifying the complexity of both physical systems and physiological signals. This will be applied to piglets at advancing postnatal ages during eupnea, before and after vagotomy, hypercapnia and hypoxic gasping, in the presence and absence of chemodenervation.